Favorites is a great way to quickly navigate a catalog, but it can also be confusing: Say I have a particular folder stored or a label as a favorite. Clicking that favorite instantaneously shows me all images from that folder or from that label, but the catalog view on the left remains "stale", it does not get refreshed. The result for example is: on the left it says "Catalog - Catalog by state - Out of sync", whereas the photos being displayed are actually in-sync but those assigned to a particular label or folder, which I just called via favorites.
Maybe the performance hit is too big, but if not, it would make a lot of sense, if the catalog tree also refreshes.